United States
'''United States''' The United States of America (USA), commonly referred to as the United States (US), America, the States, or the North American Union, is a federal republic consisting of 102 states, 16 territories, and 4 federal districts At million square miles (9.83 million km2) in total and with around million people, the United States is the largest country by total area and third largest by population. It is one of the world's most ethnically diverse and multicultural nations, the product of large-scale immigration from many countries, Amerindian and European Mixes, and the Unification. The geography and climate of the United States is also extremely diverse, and it is home to a wide variety of wildlife. Paleo-indians migrated from Asia to what is now the U.S. mainland around 15,000 years ago, with European colonization beginning in the 16th century. The United States emerged from 13 British colonies located along the Atlantic seaboard, British colonies in Canada and Australia, and part of Spain’s colony (New Spain). Disputes between Great Britain and Mexico vs. these colonies led to the American Revolution for America, the Mexican Revolution for Mexico, and a peaceful separation for Canada and Australia. On July 4 1776 (America), January 1 1901 (Australia), July 1 1867(Canada), and September 16 1810 (Mexico) each of the original nations declared their independence. The ensuing wars ended with the recognition of independence of the United States from the Kingdom of Great Britain and Mexico from Spain. And the first was the first successful war of independence against a European colonial empire. The current Constitution was first adopted on September 17, 1787, but later revised and ratified by Mexican, Canadian, and Australian states. The first 10 amendments, collectively named the Bill of Rights, were ratified in 1791 and guarantee many fundamental civil rights and freedoms. Driven by the doctrine of manifest destiny, the United States embarked on a vigorous expansion across North America throughout the 19th century and once again in the early to mid 21st Century. This involved displacing native tribes, acquiring new territories, and gradually admitting new states. The American Civil War ended legal slavery in the country. By the end of the 19th century, the United States extended into the Pacific Ocean, and its economy was the world's largest. The Spanish–American War and World War I confirmed the country's status as a global military power. The United States emerged from World War II as a global superpower, the first country with nuclear weapons, and a permanent member of the United Nations Security Council. The end of the Cold War and the dissolution of the Soviet Union left the United States as the sole superpower. The Unification transformed the already large and powerful nation into one that was the largest and the most powerful by a long shot. The United States is a developed country and has the world's largest national economy, with an estimated GDP of 23% of global nominal GDP and 19% at purchasing-power parity. The economy is fueled by an abundance of natural resources and the world's highest worker productivity, with per capita GDP being .While the U.S. economy is considered post-industrial, it continues to be one of the world's largest manufacturers. The country accounts for % of global military spending, being the world's foremost economic and military power, a prominent political and cultural force, and a leader in scientific research and technological innovation. History ''Further Information: History of Australia, History of America, History of Canada, and History of Mexico.'' Geography, Climate, and Environment ''Further Information:'' Geography of North America, Geography of Oceania North America occupies the northern portion of the landmass generally referred to as the New World, the Western Hemisphere, the Americas, or simply America (which, less commonly, is considered by some as a single continent with North America a subcontinent).North America's only land connection to South America is at the Isthmus of Panama. The continent is delimited on the southeast by most geographers at the Darién watershed along the Colombia-Panama border, placing all of Panama within North America. Alternatively, some geologists physiographically locate its southern limit at the Isthmus of Tehuantepec, Mexico, with Central America extending southeastward to South America from this point. The Caribbean islands, or West Indies, are considered part of North America. Before the Central American isthmus was raised, the region had been underwater. The islands of the West Indies delineate a submerged former land bridge, which had connected North America and South America via what are now Florida and Venezuela. The continental coastline is long and irregular. The Gulf of Mexico is the largest body of water indenting the continent, followed by the Hudson Bay. Others include the Gulf of Saint Lawrence and the Gulf. There are numerous islands off the continent's coasts; principally, the Arctic Archipelago, the Bahamas, Turks & Caicos, the Greater and Lesser Antilles, the Aleutian Islands (some of which are in the Eastern Hemisphere proper), the Alexander Archipelago, the many thousand islands of the British Columbia Coast, and Newfoundland. Greenland, the world's largest, is on the same tectonic plate (the North American Plate) and is part of North America geographically. In a geologic sense, Bermuda is not part of the Americas, but an oceanic island which was formed on the fissure of the Mid-Atlantic Ridge over 100 million years ago. The nearest landmass to it is Cape Hatteras, North Carolina. However, Bermuda is often thought of as part of North America, especially given its historical, political and cultural ties to Virginia and other parts of the continent. The vast majority of North America is on the North American Plate. Parts of western Mexico, including Baja California, and of California, including the cities of San Diego, Angeles and part of San Francisco, lie on the eastern edge of the Pacific Plate, with the two plates meeting along the San Andreas fault. The southernmost portion of the continent and much of the West Indies lie on the Caribbean Plate, whereas the Juan de Fuca and Cocos plates border the North American Plate on its western frontier. The continent can be divided into four great regions (each of which contains many subregions): the Great Plains stretching from the Gulf of Mexico to the Canadian Arctic; the geologically young, mountainous west, including the Rocky Mountains, the Great Basin, California and Alaska; the raised but relatively flat plateau of the Canadian Shield in the northeast; and the varied eastern region, which includes the Appalachian Mountains, the coastal plain along the Atlantic seaboard, and the Florida peninsula. Mexico, with its long plateaus and cordilleras, falls largely in the western region, although the eastern coastal plain does extend south along the Gulf. The western mountains are split in the middle into the main range of the Rockies and the coast ranges in California, Oregon, Washington, and British Columbia, with the Great Basin—a lower area containing smaller ranges and low-lying deserts—in between. The highest peak is Denali in Alaska. 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